Question

1) When we say calcium reacts readily with cold water, it means the reaction is moderately fast?

2) When we react Fe with dilute HCl, we get FeCl2 & H2. Why won't we get FeCl3?

3) Similarly, when we react Fe with CuSO4, displacement reaction occur to give FeSO4 & Cu. Why won't we get
Fe2(SO4)3?

Answer 1

http://books.google.com/books?id=STxHXRR4VKIC&pg=PA312&lpg=PA312&dq=iron+oxidation+states+stability+energy&source=web&ots=EE_tKI93-T&sig=cEGksSOaiTNI9CogX7QRzRvHE0o&hl=en&ei=7t6ESaeiIImIsAPpm-29DQ&sa=X&oi=book_result&resnum=4&ct=result#PPA333,M1

see page 333 to answer the third question. The point on that page is that FeII ion is stable, even in water, and the FeIII is relatively stable. IT is a matter of free energy.
On the first question above, Yes, it is moderately fast.